The present application claims priority from Japanese application JP2017-128824 filed on Jun. 30, 2017, the content of which is hereby incorporated by reference into this application.
This relates to display devices.
Recently, displays equipped with illuminants such as organic electroluminescence have been developing (JP H09-304796A and JP 2000-030857A). Organic electroluminescence elements, which are vulnerable to moisture, are configured to be covered with a sealing film (JP 2000-030857A). To improve barrier properties, a kind of sealing film is known to have a structure where an organic layer is interposed between a pair of inorganic films.
A cap layer is technically used for gradually changing refractive indexes to improve light extraction efficiency. With a defect in the sealing film, water enters there and diffuses into the cap layer, changing the refractive index in the material of the cap layer. Then, the light extraction efficiency cannot improve.
This is to aim at curbing deterioration of the cap layer.
A display device may include a lower electrode; an electroluminescence layer on the lower electrode; an upper electrode on the electroluminescence layer; a cap layer on the upper electrode for improving light extraction efficiency; an absorbent layer on the cap layer, the absorbent layer extending from above and laterally next to the cap layer; and a sealing film on the absorbent layer.
The cap layer is prevented from deterioration by the absorbent layer provided not only above it but also laterally next to it.
Hereinafter, some embodiments will be described with reference to the drawings. Here, the invention can be embodied according to various aspects within the scope of the invention without departing from the gist of the invention and is not construed as being limited to the content described in the embodiments exemplified below.
The drawings are further schematically illustrated in widths, thickness, shapes, and the like of units than actual forms to further clarify description in some cases but are merely examples and do not limit interpretation of the invention. In the present specification and the drawings, the same reference numerals are given to elements having the same functions described in the previously described drawings and the repeated description will be omitted.
Further, in the detailed description, “on” or “under” in definition of positional relations of certain constituents and other constituents includes not only a case in which a constituent is located just on or just under a certain constituent but also a case in which another constituent is interposed between constituents unless otherwise mentioned.
The scanning signal circuit 14 is connected to a scanning signal line 30 provided for each of horizontal rows (pixel rows) of pixels and is configured for outputting a scanning signal to the selected one of the scanning signal lines 30. The scanning signal controls the thin film transistor 24.
The video signal circuit 16 is connected to a video signal line 32 provided for each of vertical columns (pixel columns) of pixels and is configured for outputting a video signal. The scanning signal circuit selects one of the scanning signal lines 30 to turn on the corresponding thin film transistor 24 and writes on the capacitor 26 the video signal output to the video signal line 32.
The thin film transistor 28 is controlled in accordance with the voltage written on the capacitor 26. The thin film transistor 28 controls a current to be supplied to the display element 20 from a driving power line 34 provided for each pixel column and connected to the power supply driving circuit 18. The display element 20 has its brightness controlled by the current control. The display element 20 is grounded on a side opposite to the thin film transistor 28.
Under the lower electrode 36 are a capacitance electrode 42 and a capacitive insulation layer 44, which constitute a capacitor 26. The capacitive insulation layer 44 is made from inorganic insulation material such as silicon nitride (SiNx). Under the display element 20 and the capacitor 26 is a planarization film 46 made from an organic insulation film such as an acrylic resin or a polyimide resin.
The lower electrode 36, which is made from metal with light reflectivity such as aluminum, extends to a bottom of the contact hole 50 in
The organic electroluminescence layer 38, which is between the upper electrode 40 and the lower electrode 36, includes a hole transport layer, a hole transport layer, a light emitting layer, an electron transport layer, and an electron injection layer. Some layers except for the light emitting layer continuously overlap with a plurality of lower electrode 36, whereas the light emitting layer is individually disposed for each lower electrode 36. The light emitting layer generates light due to recombination of holes injected from the lower electrode 36 and electrons injected from the upper electrode 40.
The upper electrode 40 is formed from a transparent conductive film such as indium tin oxide (ITO), in a widely spread shape to be a common one layer for the plurality of pixels in the display area DA. As shown in
The display device includes a cap layer 58. The cap layer 58 is on the upper electrode 40 entirely in the display area DA to improve light extraction efficiency. The cap layer 58 further extends to the peripheral area PA. The cap layer 58 has its thickness and its refractive index selected in accordance with emission intensity and emission wavelength of light from the organic electroluminescence layer 38. The cap layer serves as a protective layer for the organic electroluminescence layer 38 including the upper electrode 40. The cap layer 58 is formed from publicly known inorganic material. The material of the cap layer 58 preferably has a refractive index of 1.0 or more. The best method of forming the cap layer 58 is selected in accordance with the material thereof. The cap layer 58 generally has its thickness of 5 nm to 100 nm preferably for effective emission of light although it is not limited.
The display device has an absorbent layer 60, which may include calcium or calcium oxide. The absorbent layer 60 is on the cap layer 58. The absorbent layer 60 spreads all over the display area DA and further extends to the peripheral area PA. The absorbent layer 60 continuously extends from above and laterally next to the cap layer 58. As shown in
The absorbent layer 60 further covers the upper electrode 40 at its periphery from its side and is in contact with the upper electrode 40 at its periphery. The absorbent layer 60 entirely surrounds the upper electrode 40 and is also in contact with a layer (cathode contact 56) under the periphery of the upper electrode 40.
The absorbent layer 60 extends from above and laterally next to the organic electroluminescence layer 38. As shown in
The display device has a sealing film 62. The display element 20 is covered with the sealing film 62 for its protection. The sealing film 62 has a structure where an organic film is interposed between inorganic layers over and under it; the inorganic layer may be made from silicon nitride or silicon oxide. The sealing film 62 is on the absorbent layer 60. The sealing film extends from above and laterally next to each of the absorbent layer 60, the cap layer 58, and the organic electroluminescence layer 38. The sealing film 62 entirely surrounds each of the absorbent layer 60, the cap layer 58, and the organic electroluminescence layer 38.
The display device is not limited to the organic electroluminescence display device but may be a display device with a light-emitting element disposed in each pixel, such as a quantum-dot light-emitting diode (QLED).
While there have been described what are at present considered to be certain embodiments, it will be understood that various modifications may be made thereto, and it is intended that the appended claims cover all such modifications as fall within the true spirit and scope of the invention.
Number | Date | Country | Kind |
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2017-128824 | Jun 2017 | JP | national |